Composite tubular elements and methods of fabrication

ABSTRACT

The present invention relates to a unique fiber-reinforced metallic tubular element, along with a unique method for producing such tubular elements on a production basis. The tubular element includes a cylindrical aluminum tube surrounded by a fiber composite sleeve which includes a plurality of individual reinforcing graphite fibers oriented parallel to the longitudinal axis of the tube and uniformly positioned about the circumference of the tube. In the preferred embodiment of the invention, an isolation layer is positioned between the graphite reinforcing layer and the outer surface of the aluminum tube, and a protective covering layer of fiber material surrounds the tube and is adhered to the outer surface of the graphite reinforcing layer. In the preferred method of the present invention, a plurality of cylindrical metal tubes are coupled to one another in an end-to-end relationship by a plurality of joining plug members to form a longitudinally extending series of metal tubes. The series of metal tubes are fed along a longitudinal axis to an apparatus for applying the individual layers of the composite fiber sleeve along with a curable resin material to the tube. As the series of tubes having the cured composite sleeve thereon exits the apparatus, the tubes are severed at each of the joining plugs to produce a plurality of individual fiber reinforced tubular elements. Alternate methods of manufacturing the fiber reinforced tubular elements are also disclosed. In the preferred embodiment of the invention, the fiber reinforced tubular element is utilized as a vehicle drive shaft.

This application is a continuation of Ser. No. 857,717, filed Apr. 30,1986, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates generally to fiber reinforced tubularelements such as vehicle drive shafts and, in particular, to a graphitereinforced aluminum drive shaft and a method for producing such a driveshaft.

Over the past decade, there has been an ongoing endeavor by the industryto reduce the weight of vehicles in order to improve fuel economy. Inaddition to downsizing and redesigning vehicles to make the mostefficient use of the available space, a great deal of attention has beengiven to constructing various vehicular components of lighter weightmaterials. For example, in the area of drive shafts, it has beenproposed to replace conventional steel drive shafts with lighter weightaluminum tubes. However, depending on the length of the drive shaft, andthe maximum speed at which the drive shaft is to be rotated, vibrationproblems can arise.

While typically the tubular steel or aluminum drive shafts are adequateto transmit the torsional forces involved, there is a tendency for ashaft to "whip" or resonate mechanically when the shaft reaches acertain vehicle speed, typically referred to as a critical speed.Consequently, in order to overcome the critical speed limitations ofsingle long drive shafts, typically multiple sections of shafts areemployed. In these instances, adjacent individual drive shaft sectionsare connected to one another by means of a universal joint assemblywhich in turn is supported by a bearing mounting unit affixed to thevehicle frame.

In order to accommodate a longer drive shaft such that the universaljoint assemblies and the bearing mounting units can be eliminated, ithas been proposed to reinforce metal tubes with a fiber reinforcedsleeve portion to increase the axial stiffness of the shaft withoutsubstantially increasing its weight. For example, U.S. Pat. Nos.4,131,701; 4,173,670; and 4,214,932 all disclose fiber compositealuminum drive shafts wherein aluminum tubes are wrapped withalternating layers of resin-impregnated woven fiberglass cloth andresin-impregnated fiber reinforcing sheets. The reinforcing sheets arecomprised of continuous unindirectional graphite fiber layers, with thegraphite fibers arranged at angles between ±5° to ±20° with respect tothe longitudinal axis of the tube. Another approach to reinforcing atubular metallic drive shaft is disclosed in U.S. Pat. No. 4,272,971,which discloses a drive shaft wherein the fiber reinforcing layer isapplied to the inside surface of an aluminum tube.

While the above-discussed fiber-reinforced drive shafts havesatisfactory operating characteristics, they have been found difficultand expensive to produce on a high volume production basis.

SUMMARY OF THE INVENTION

The present invention relates to a unique fiber reinforced aluminumdrive shaft, along with a unique method for producing such drive shaftson a production basis.

The drive shaft of the present invention includes a cylindrical metaltube having a longitudinal axis which, in the preferred embodiment ofthe invention, is typically constructed of aluminum. An isolation layerof cloth material surrounds the aluminum tube and is adhered to theouter surface of the tube. A reinforcing fiber layer also surrounds thetube and is adhered to the outer surface of the isolation layer. Inaccordance with the present invention, the reinforcing fiber layerincludes a plurality of individual reinforcing graphite fibers which areorientated parallel to the longitudinal axis of the tube and areuniformly positioned about the circumference of the tube. In the abovediscussed prior art, the graphite fibers were specifically locatednon-parallel with the longitudinal axis. Finally, the drive shaftincludes a covering layer of fiber material surrounding the tube andadhered to the outer surface of the reinforcing fiber layer.

The present invention includes a unique approach to producing the fiberreinforced drive shafts on a production basis. In the method of thepresent invention, a plurality of cylindrical metal tubes each having alongitudinal axis are coupled to one another in an end-to-endrelationship by a plurality of joining plastic plug members to form alongitudinally extending series of metal tubes. The series of metaltubes are fed along a longitudinal path through an apparatus forapplying the individual layers of the composite fiber sleeve to thetube.

Initially, the isolation layer of cloth material is applied around theouter surface of the tube. Next, the plurality of individual reinforcingfibers are applied about the circumference of the tube such that theindividual reinforcing fibers are parallel to the longitudinal axis ofthe tubes. Next, the covering layer of fiber material is applied aroundthe outer surface of the reinforcing fiber layer.

While the individual layers are being applied to the tube, a vinylesterliquid resin material is applied to saturate the individual layers, andthe drive shaft having the saturated layers applied thereto is thenpassed through a heated forming die wherein the liquid resin is cured tofirmly adhere the individual layers to the series of tubes. As theseries of tubes having the cured composite sleeve thereon exits theapparatus, the tubes are severed at each of the joining plugs to producea plurality of individual fiber reinforced drive shafts. In someinstances, wherein a connecting member such as a yoke portion or asplined shaft is to be welded to the end of the drive shafts, it hasbeen found desirable to strip a selected end portion of the compositereinforcing layer from the drive shaft to prevent heat damage to the endof the composite sleeve during the welding operation.

The present invention also concerns alternate methods of manufacturingthe drive shafts.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, willbecome readily apparent to one skilled in the art from the followingdetailed description of the preferred embodiments of the invention whenconsidered in light of the accompanying drawings, in which:

FIG. 1 is a side elevational view of a fiber reinforced compositetubular element of the present invention, shown for use as a driveshaft;

FIG. 2 is a fragmentary sectional view taken along line 2--2 in FIG. 1and showing the individual layers which constitute the preferredembodiment of the fiber composite sleeve;

FIG. 3 is a schematic diagram showing one method of fabricating thefiber composite tubular element of the invention on a continuous basiswherein the fiber composite sleeve is formed and cured about a series ofindividual metal tubes temporarily joined together and moving in alongitudinal path;

FIG. 4 is a side elevational view of a composite fiber reinforcedtubular element produced according to the method schematicallyillustrated in FIG. 3;

FIG. 5 is a schematic drawing which illustrates an alternate method ofassembly of the drive shaft wherein individual previously formed andcured fiber composite sleeves are slipped over and adhesively secured toan associated metal tube; and

FIG. 6 is a schematic drawing which illustrates a further alternatemethod of manufacture wherein a preformed and uncured, resin-saturatedfiber reinforcing sleeve is slipped over a metal tube member andsubsequently cured thereon.

cl DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, there is shown a drive shaft 10 which utilizesa composite tubular element embodying the features of the presentinvention. The drive shaft 10 includes an outer composite fiberreinforcing sleeve 12 which surrounds and is attached to the exterior ofa cylindrical metal tube 14. As illustrated, first and second connectingmembers 16 and 18, which are shown as yoke portions, are connected toopposite ends of the metal tube 14 for coupling the drive shaft betweena drive member (not shown) and a driven member (not shown). While theconnecting members are shown as yoke portions for connection to anassociated universal joint assembly (not shown), it will be appreciatedthat other types of connecting members such as, for example, a splinedshaft end can be used.

The connecting members 16 and 18 are typically secured to the ends ofthe metal tube 14 by a welding operation. To prevent heat damage to thecomposite sleeve 12 when the connecting members are attached, the endsof the reinforcing sleeve 12 are spaced inwardly from the ends of themetal tube 14 to provide exposed metal end portions 20 and 22. As willappear more fully below, in the preferred method of manufacture, thereinforcing sleeve 12 is initially formed along the entire length of themetal tube 14 and is subsequently stripped from the end portions 20 and22 by severing it circumferentially with a saw, and peeling it off. Inother methods of manufacture, the reinforcing sleeve 12 is formed sothat it initially does not cover end portions 20 and 22.

Turning now to FIG. 2, there is shown a cross-section through the tube14 and the preferred embodiment of the composite reinforcing sleeve 12.Typically, the metal tube 14 is a cylindrical aluminum tube fabricatedin a conventional manner. The length, diameter, and wall thickness ofthe tube, along with the particular aluminum alloy from which the tubeis formed, may vary from application to application, depending on theparticular power transmission requirements of the drive shaft. In anyevent, the use of the composite reinforcing sleeve 12 having thespecific construction of the present invention has been found tosufficiently increase the axial stiffness of the aluminum tube such thatweight of the tube can be substantially reduced as compared with atubular aluminum drive shaft without the reinforcing sleeve.

The composite reinforcing sleeve 12 basically consists of threesections: an isolation layer 32, a fiber reinforcing layer 34, and acovering layer 36. As will be discussed, in the preferred method ofmanufacture, the individual layers of the sleeve 12 are bonded to oneanother and the tube by a vinylester resin.

The isolation layer 32 includes individual layers 32a, 32b, and 32c. Thefirst isolation layer 32a is composed of a plurality of longitudinallyextending threads of string material equally spaced about thecircumference of the tube. This layer is not essential to thefunctioning of the invention but, as will be discussed, is provided as avisual indicator to avoid contact of a saw blade (not shown) with themetal tube 14 when stripping the end portions of the reinforcing sleeve12 as previously described. In the preferred embodiment of the driveshaft, the layer 32a consists of eight longitudinally extendingpolyester strings equally spaced about the circumference of the tube.

The second isolation layer 32b is composed of individual strips of athin screen-like cloth material which extend longitudinally and haveoverlapping lateral edge portions to completely surround the tube. Thislayer functions to isolate the fiber reinforcing layer 34, which istypically graphite, from the aluminum tube 14, since it has been foundthat direct contact between graphite and aluminum results in undesirableelectrolytic corrosion. The exact width of the individual strips will bedependent on the number of strips utilized, along with the outsidediameter of the tube. While the number of strips of cloth material whichare utilized to surround the tube can vary from application toapplication, in the preferred embodiment, four individual strips ofcloth material are utilized.

The third isolation layer 32c is similar to the first layer 32a, and iscomprised of a plurality of longitudinally disposed threads of polyesterstring uniformally spaced about the circumference of the tube. In thepreferred embodiment, eight threads are used. Again, this is not anessential layer, but is provided to form and hold the strips of clothmaterial in place on the metal tube 14. It will be appreciated that,while the isolation string layers 32a and 32c are shown in FIG. 2 asspacing the isolation cloth layer 32b from both the tube 14 and thefiber reinforcing layer 34, there is actually contact between the layer32b and the tube 14 and between the layer 32b and the reinforcing layer34 in the regions between the spaced apart longitudinally extendingthreads.

The fiber reinforcing layer 34 is typically comprised of graphite andincludes a plurality of individual and independent reinforcing fiberstrands or "tows" which, in accordance with the present invention, arepreferably located parallel to the longitudinal axis of the tube, anduniformly positioned about the isolation layer 32. Each tow consists ofa predetermined number of longitudinally disposed, individual graphitefibers. The exact number of tows of graphite which are utilized willdepend on the number of individual fibers located in each tow and theoverall amount of reinforcing which is desired. In one preferredembodiment, 115 longitudinally disposed tows of graphite fibers areutilized, with each tow being composed of 36,000 individual fibers ofgraphite.

The covering or protective layer 36 includes individual layers 36a, 36b,and 36c, and functions as a means for retaining the longitudinalgraphite strands of the layer 34 adjacent the metal tube 14. The firstcovering layer 36a is comprised of a circumferential wrapping offiberglass strands. The number of circumferential wrappings per givenlength of the tube will be dependent on the amount of graphite which hasbeen applied to the tube, along with the number of individual glassfibers included in each strand. In the preferred embodiment, each strandis composed of 1,800 continuous glass filaments, and is wrapped aboutthe tube to produce twenty wraps per longitudinal inch.

The second covering layer 36b is another circumferential wrapping,similar to that of the first covering layer 36a, but with polyesterstring, of a type similar to that used in the first and third isolationlayers 32a and 32c. It should be noted that the layers 36a and 36b,although illustrated as overlying layers, do not visually form separatelayers, since the strands of one wrapping will typically fall in betweenthe strands of the other, so that layers 36a and 36b appear visually asa single layer.

The third covering layer 36c, which is the outermost layer of the sleeve12, is applied similarly to and is identical in material characteristicsto that of the isolation layer 32b, and provides an outer cloth coveringwhich produces a smooth outer surface on the drive shaft.

Turning now to FIG. 3, there is shown schematically an apparatus 40 forforming composite tubular elements of the type illustrated in FIG. 2 ona continuous basis. As shown in FIG. 3, a plurality of metal tubes,shown as 14a, 4b, 14c, 14d, are interconnected in an end-to-endrelationship by a plurality of plug members 42. The plug members 42,which typically are constructed of a plastic material, are shown asdouble-ended, with a centrally located protruding annular flange portion44 having an outer diameter greater than the outside diameter of thetubes. As will be discussed, the protruding flange portion 44, aftereach layer of the composite sleeve has been applied and cured on thetubes, provides an annular raised portion in the sleeve which functionsas a visual reference to define the specific location at which the tubesmust be sawed apart.

The apparatus 40 includes a plurality of individual application stationswhich, as discussed in more detail below, are utilized to apply thevarious materials required to form the composite fiber sleeve on thealuminum tube. The apparatus also includes a pair of pulling rollers 46and 48 for pulling the longitudinally extending series of tubes throughthe apparatus along a longitudinally extending path at a predeterminedspeed.

As shown in FIG. 3, at first station 50, the first isolation layer 32aof longitudinally extending, circumferentially spaced apart string isapplied. String from a plurality of rolls 52 passes through a guidemeans 54 and an application means 56, which may be pulleys or the like,into place on the tube 14. Although four rolls are shown, eight rollsare used in the preferred embodiment of the invention. Also, while shownas tapered rolls or spools, the spools used are preferably of thecenter-feed type, so that the last turn is on the outside, andadditional rolls can be connected without interrupting the process.

Then, at a second station 58, the second isolation layer 32b of stripsof cloth material is applied. As shown, the layer 32b is applied in foursegments. At the second station 58, the material of the second layer 32bis applied from rolls 60 and 62. While not shown in the drawings, therolls 62 are preferably located along a line which is perpendicular tothe line along which the rolls 60 are located. The individual strips areurged into conformance with the shape of tube 14 by a conical preformer64.

Next, at a third station 66, the third isolation layer 32c of string isapplied to form the cloth layer 32b around the tube 14. As with thefirst station 50, the string from a plurality of rolls 68 passes througha guide means 70 and an application means 72 into position around thetube 14.

At a fourth station 74, approximately half of the fiber reinforcinglayer 34 is applied. A set of rolls 76, although shown as six in numberfor simplicity, actually number approximately half of the total numberof graphite tows to be applied. The tows supplied from the rolls 76 passthrough individual apertures in a forming ring 78 into conformance withthe shape of the tube 14. Then, at a fifth station 80, a resin mixtureis supplied from a tank 82 through a line 84 to a dispensing end 86,from which it coats the first half of the fiber reinforcing layer 34 andthe underlying isolation layer 32.

The resin mix contained in the tank 82 is preferably a vinylester resinmix of the type available under the trade name Derakane. A suitableresin mixture is available from Dow Chemical of Joliet, Ill. under partnumber 411-35. In addition, any conventional resin mixture may be used,although it should be selected from among those that remain flexibleafter curing. Although not shown in the drawings, a catalyst or hardenercan be mixed with the resin mixture shortly before application of themixture to the partially formed sleeve.

At a sixth station 88, the remainder of the desired number of graphitetows are applied from a set of rolls 90 through a forming ring 92 intoconformance with the tube 14 and, at a seventh station 94, are againcoated with the resin mixture from the tank 82, through a line 96 and adispensing end 98.

An eighth station 100 and a ninth station 102 include a spinner head 104having rolls 106 and 108 for circumferentially wrapping covering layers36a and 36b respectively. Of course, more than one such spinner head 104may be provided, and more than a single roll can be used to apply thelayers 36a and 36b. As illustrated, the head 104 contains the fiberglassmaterial of the first covering layer 36a on the roll 106 and thepolyester string material of the second covering layer 36b on the roll108. As previously described, the layers 36a and 36b are circumferentialwrappings which, in the preferred embodiment, are applied at a rate ofapproximately twenty per inch. At a tenth station 110, the resin mixfrom the tank 82 is again applied, through a line 112 and a dispensingend 114.

Then, at an eleventh station 116, the final layer, the third coveringlayer 36c, is applied. A set of rolls 118 contain cloth materialidentical to that contained by the rolls 60, which material is urgedinto conformance with the tube 14 by a conical performer 120. A set ofrolls 122 contain cloth material identical to that contained on therolls 62, which material is urged into conformance with the tube 14 by aconical entrance 124 of a heated forming die 126. As was the case withthe rolls 60 and 62, the rolls 118 and 122 are preferably located alonglines perpendicular to one another. The forming die 126 not only formsthe surface of the continuous drive shaft assembly, but also providesappropriate heat input to effect a rapid cure of the resin mixture asthe series of drive shafts are pulled through the apparatus 40.

The continuous chain of composite tubular elements 10 is then cut apartat protruding flange portions 48, and stripped in a manner as describedabove to form exposed metal end portions 20 and 22, to which appropriateconnecting members can be attached by conventional welding. Thecomposite tubular element produced by the method of FIG. 3 is shown inFIG. 4 prior to the attachment of the connecting members.

It will be appreciated that other methods can be utilized to produce afiber-reinforced aluminum drive shaft embodying the principal featuresof the present invention. For example, FIG. 5 schematically illustratesa method wherein a stiff, performed, precut and previously curedreinforcing sleeve 130 of a predetermined length is provided, with aninternal diameter slightly larger than the external diameter of themetal tube 14. As illustrated in FIG. 5, the reinforcing sleeve 130 isslipped into position over a metal tube 132, to which a layer of glue134 has been applied.

Various types of glues or bonding agents may be used for the glue 134.One such structural adhesive which can be used is commercially known asMetalbond 1133, and is an elastomer modified epoxy material sold by theNarmco division of Celanese Corp, New York, N.Y.. Such adhesives may beapplied by brushing or spraying.

FIG. 6 illustrates schematically a further alternate method of making acomposite tubular element according to the invention, in which afiber-reinforced sleeve 140 saturated with uncured resin, but made toappropriate length, is slipped over a metal tube 142 and is subsequentlycured to bond the sleeve 140 to the metal tube 142. If desired, anappropriate structural adhesive may be used to assist in bonding thesleeve to the tube. In FIG. 6, the fiber-reinforced sleeve 140 is formedon a mandrel 148, and is saturated with resin from a tank 150 through aline 152 and a dispensing end 154, or by any other convenient means,such as brushing or spraying. As illustrated, the reinforcing sleeve 140includes three layers, an inner layer of isolation material applied byrolls 156, an intermediate layer of longitudinally extending reinforcingfiber applied by rolls 158, and an outer layer of covering materialapplied by rolls 160.

As shown in FIG 6, there is a supply of metal tubes 142, onto each ofwhich a reinforcing sleeve member 140 is placed by sliding it offmandrel 148 and onto the tube 142, wherein it is urged into position byapplying circumferentially forces 162 in any convenient manner, such asby drawing a forming die over it. Then, the reinforcing member 140 iscured in place on the metal tube 142, either by the passage of timewithout application of heat, or by the application of heat in anyconvenient manner.

The precise embodiment of the reinforcing sleeve used in the methodsillustrated in FIGS. 5 and 6 may differ from the construction shown inFIG. 2 and produced by the method of FIG. 3. For example, the first andthird isolation layers 32a and 32c of FIG. 2, which provide a visualindicia for stripping the ends of the sleeve in the method of FIG. 3,would not be required in the methods of FIGS. 5 and 6, since thereinforcing sleeves are formed to length before application to the metaltube. In addition, in some instances, the second isolation layer 32b mayalso not be necessary, since the glue used to retain a previously formedcured or uncured reinforcing sleeve to a metal tube may by itselfprovide a suitable isolation layer between the graphite and thealuminum. Also, the outer most covering layer 36c of FIG. 2, which isprovided to form a smooth exterior surface is not an absolute necessity,nor is the use of two different materials, shown as covering layers 36aand 36b to retain the primary reinforcing fiber layer 34 in place.

In accordance with the provisions of the patent statutes, the compositetubular element of the present invention, along with the methods ofproducing the tubular element, have been illustrated and described inits preferred embodiments. However, it will be appreciated that numerousmodifications and variations of the disclosed invention will be apparentto one skilled in the art, including re-arrangement in the ordering oflayers and the addition or omission of layers, and may be made withoutdeparting from the scope of the attached claims.

What is claimed is:
 1. A composite fiber reinforced vehicle drive shaftcomprising:an elongate cylindrical metal tube having a longitudinalaxis; a separate metal connecting member secured to each end of saidmetal tube and adapted to be coupled to a vehicle drive train component;a cylindrical reinforcing sleeve secured to a cylindrical surface ofsaid metal tube and extending longitudinally along said tube betweensaid connecting members, said reinforcing sleeve including an isolationlayer adjacent said cylindrical surface of said tube, a reinforcingfiber layer adjacent said isolation layer, and a covering layer adjacentsaid reinforcing fiber layer; a cured resin impregnated into and forminga matrix for securing said isolation, fiber reinforcing, and coveringlayers to each other; said isolation layer including a plurality ofstrips of flexible sheet material contacting said metal tube andextending longitudinally along said tube with adjacent ones of saidstrips having overlapping longitudinal edge portions to prevent directcontact between said reinforcing fiber layer and said cylindricalsurface of said tube; said reinforcing fiber layer increasing thestiffness of said metal tube and being formed of a plurality of separatetows individually and uniformly circumferentially positioned on saidisolation layer in parallel relationship to said longitudinal axis ofsaid tube, each of said tows including a plurality of continuousreinforcing fibers; and said covering layer including a string materialcircumferentially positioned on said reinforcing fiber layer formaintaining said reinforcing fibers adjacent said isolation layer.
 2. Avehicle drive shaft as defined in claim 1 wherein said covering layerincludes a plurality of second strips of flexible sheet material appliedto said string material and extending longitudinally along said tubewith adjacent ones of said second strips having overlapping longitudinaledge portions.
 3. A vehicle drive shaft as defined in claim 1 whereinsaid cylindrical surface of said tube is an outer cylindrical surface.4. A vehicle drive shaft as defined in claim 1 wherein said reinforcingfiber layer includes graphite fibers.
 5. A vehicle drive shaft asdefined in claim 4 wherein said metal tube is made of aluminum.
 6. Acomposite fiber reinforced vehicle drive shaft comprising:an elongatecylindrical metal tube having a longitudinal axis; a separate metalconnecting member secured to each end of said metal tube and adapted tobe coupled to a vehicle drive train component; a cylindrical reinforcingsleeve secured to a cylindrical surface of said metal tube and extendinglongitudinally along said tube, said reinforcing sleeve including anisolation layer adjacent said cylindrical surface of said tube, areinforcing fiber layer adjacent said isolation layer, and a coveringlayer adjacent said reinforcing fiber layer; a cured resin impregnatedinto and forming a matrix for securing said isolation, fiberreinforcing, and covering layers to each other; said isolation layerproviding a barrier to prevent direct contact between said reinforcingfiber layer and said cylindrical surface of said tube; said reinforcingfiber layer increasing the stiffness of said metal tube and being formedof a plurality of separate tows individually and uniformlycircumferentially positioned on said isolation layer in parallelrelationship to said longitudinal axis of said tube, each of said towsincluding a plurality of continuous reinforcing fibers; and saidcovering layer including a string material circumferentially positionedon said reinforcing fiber layer for maintaining said reinforcing fibersadjacent said isolation layer.
 7. A vehicle drive shaft as defined inclaim 6 wherein said cylindrical surface of said tube is an outercylindrical surface.
 8. A vehicle drive shaft as defined in claim 6wherein said isolation layer comprises a plurality of strips of flexiblesheet material contacting said metal tube and extending longitudinallyalong said tube with adjacent ones of the strips having overlappinglongitudinal edge portions to prevent direct contact between saidreinforcing fiber layer and said cylindrical surface of said tube.
 9. Avehicle drive shaft as defined in claim 8 wherein said isolation layeralso includes inner and outer layers respectively disposed on oppositesides of said strips, each of said inner and outer layers comprising aplurality of string members extending longitudinally along said tube andcircumferentially spaced apart about said longitudinal tube axis.
 10. Avehicle drive shaft as defined in claim 6 wherein said covering layercomprises a string material circumferentially applied to saidreinforcing fiber layer for maintaining said reinforcing fibers adjacentsaid isolation layer.
 11. A vehicle drive shaft as defined in claim 10wherein said string material includes continuous glass filaments.
 12. Avehicle drive shaft as defined in claim 11 wherein said covering layeralso includes a polyester string material applied circumferentially tosaid reinforcing fiber layer.
 13. A vehicle drive shaft as defined inclaim 12 wherein said covering layer also includes a layer of clothmaterial applied to said circumferentially applied string materials. 14.A vehicle drive shaft as defined in claim 10 wherein said covering layeralso includes a layer of cloth material applied to saidcircumferentially applied string material.
 15. A vehicle drive shaft asdefined in claim 14 wherein said layer of cloth material includes aplurality of strips of flexible sheet material extending longitudinallyalong said tube with adjacent ones of said strips having overlappinglongitudinal edge portions.
 16. A vehicle drive shaft as defined inclaim 6 wherein said reinforcing fiber layer includes graphite fibers.17. A vehicle drive shaft as defined in claim 6 wherein said metal tubeis made of aluminum.